Gear lubricant



Patented Aug. 22, 1939 UNITED STATES PATENT OFFICE GEAR LUBRICANT NoDrawing. Application September 4, 1937, Serial No. 162,549

1 Claim.

In the manufacture of lubricants for heavy duty gearing, difliculty isoften experienced in obtaining sufficient adhesion of the lubricant tothe metal of the gears. This is manifested in a tendency for the greaseor highly viscous oil to slide off of the contacting faces, leaving onlya very thin film which is insufficient to maintain itself against thehigh pressures encountered. Where the lubricant does not adhere to themetal sur face with sufficient tenacity there is danger of the thinfilms being penetrated by the engaging metal surfaces, which are thusallowed to come into metal to metal contact and are rapidly damaged ordestroyed.

These lubricants may be compounded greases, or they may be heavy andhighly viscous residuals from petroleum oils more or less free fromasphalt, or for rough open gears they may even consist of crude oilresidua containing or blended with petroleum asphalt.

I have discovered that lubricants of this general type, in which coloris immaterial and which are to be subjected to high pressures, may havetheir adhesiveness for metals greatly increased by dissolving in andblending with them the resin remaining from the steam distillation ofacidtreated pressure still naphthas.

The motor fuel fraction from pressure cracking operations is, as is wellknown, customarily redistilled and then treated with small doses ofsulfuric acid, after which it is neutralized with alkali and waterwashed. The treated distillate is then again distilled in a current ofsteam to yield cracked gasoline.

The residue from this operation is a brownish or blackish oil or tar,which I distil further, in a current of steam, to obtain the resin whichI use for the above stated purpose. The distillation should be carriedat least to the point at which the residuum in the steam still is highlyviscous when cold, and is preferably carried on until the residuumassumed the form of a hard and very brittle resin. This resin isfusible, is soluble in petroleum oils when heated, and has acharacteristic aromatic odor. The yield will depend to some extent onthe degree to which the original pressure distillate is cracked and alsoon the amount of acid used in its treatment, and will also vary with thedepth to which the steam distillation is carried. Ordinarily the yieldwill be from 2% to 4% or more of the quantity of treated distillatetaken for the second distillation.

These resins may be added to heavy duty lubricants in proportionsranging from 5% to 20% of the total volume, and will be found to yield alubricant of very superior tackiness and adhesiveness, and one in whichthese qualities persist over long periods of use. In these respects theabove described resins will be found far superior to the asphalts whichhave heretofore been used for the same purpose.

The term cracked petroleum distillate is used in the claims to describea distilled fraction obtained as a product of a cracking process, andmay not be taken to mean the synthetic crude produced by cracking adistillate nor any product containing substantial amounts of theresiduum from such a synthetic crude.

I claim as my invention:

A gear lubricant comprising a heavy petroleum residuum with from 5% to20% of the resin remaining after distilling acid treated and neutralizedcracked petroleum distillate, said resin being hard and brittle, of ablack color, soluble in heated petroleum oils and having an aromaticodor and the property of imparting adhesiveness to petroleum lubricants.

GERALD M. FISHER.

